The present invention relates to a fine-patterned thick film conductor structure having high circuit density and high reliability, and a method for manufacturing the same.
The fine-patterned thick film conductor structure has been required in the fields of small size coils, high package density connectors and high circuit density wirings in which a high magnitude of current is used. In the manufacture of a coil, a wire winding method is usually used but it is difficult to manufacture a small size coil by this method or the wire wound small size coil manufactured by this method has a variance in the winding. A printed coil having copper foils of 35 .mu.m thickness etched cannot provide a fine pattern because of side etching which extends twice as long as the thickness of the etched film, and it provides a pattern of 2-3 lines/mm at most. It is thus difficult to manufacture the small size coil by this method. This technique is disclosed in the U.S. Pat. No. 3,269,861, for example.
A fine-patterned thin film conductor structure can be manufactured by photoetching a very thin copper foil or additive method by photoforming. However, when it is thickened by ordinary electroless plating method of electroplating method, shortcircuiting occurs due to the side-thickening so that the fine-patterned thick film conductor structure is not produced. While a thick film plating method using walls to prevent side-thickening of thick plating has been proposed, it is not easy to form the thick-film walls on the fine-patterned conductor structure. The examples are described in Japanese Patent Applications Laid-Open Nos. 53-139175 and 53-140577.
However, as the miniaturization of motors for use in cassette tape recorders or VTR's (video tape recorders) has been developed, the development of fine coils having thick film fine patterns of 10-20 lines/mm has been required.
While the fine-patterned thick film conductor structures having circuit density of 5 lines/mm or more and film thickness of 35 .mu.m or more have been frequently required, no product having acceptable characteristics has been developed.